using System;

using System.Linq;

​

var sequence = new DayResponse[] {

    new() { Date = new DateTime(2000, 01, 01), Priority = 1},

    new() { Date = new DateTime(2001, 01, 01), Priority = 2},

    new() { Date = new DateTime(2001, 01, 01), Priority = 5},

};

​

var distinct = sequence.GroupBy(d => d.Date).Select(g => g.MinBy(d => d.Priority));

​

foreach (var x in distinct)

{

    Console.WriteLine($"DayResponse: Date = {x.Date}, Priority = {x.Priority}");

}

​

public class DayResponse

{

    public DateTime Date { get; set; }

    public int Priority { get; set; }

}

​